In routers and other network devices, queuing stages are typically used to control and buffer the data being routed. The buffers of such queuing stages are of necessity at least as large as the largest data block to be buffered. Buffers of 16 MB (megabytes) or larger are common.
These buffers are often realized in dynamic random-access memory (DRAM) chips to maintain buffering speed and data throughput. Queuing stages utilizing such DRAM buffers typically consume a significant amount of power. One such state-of-the-art device (as of the time of this discussion) consumes in excess of 13 watts per port, i.e., per queuing stage. The consumption of power generates heat, and that heat must be dissipated.
In many installations, large numbers of queuing stages are used. The power consumed in such an installation may generate a considerable amount of heat. A considerable effort may therefore be required to dissipate the generated heat.
A typical land-based Internet server installation, for example, may use a plurality of conventional equipment racks to house routers. Experience has shown that each such rack may safely dissipate up to 10 kilowatts using conventional forced-air cooling. If more than 10 kilowatts is to be dissipated, then exotic heat dissipation techniques may become necessary (e.g., liquid or cryogenic cooling).
Density is an important factor for functionality of operation. The more queuing stages that can be placed in a given location, the easier it is to connect, operate, and maintain the system. In the state-of-the-art system discussed hereinbefore, 36 queuing stages may be incorporated into a single rack panel (a single chassis), and 6 panels may be incorporated into a single equipment rack. This produces a power consumption in excess of 2.8 kilowatts per rack.
Queuing stages do not operate in isolation. Associated components, such as interface modules, are typically required. In practice, the queuing stages occupy approximately half of the rack, with the associated components occupying the remainder. These associated components will often more than double the power consumption. In such installations, total power consumed per rack is typically between one-half and two-thirds of the maximum allowable rack power.
Exotic cooling systems, such as liquid or cryogenic cooling systems, may allow a significant increase in rack-component density. Unfortunately, such exotic cooling systems present several problems. Exotic cooling systems all tend to be complex thermodynamic systems. These systems may include pumps, compressors, condensers, coolant storage tanks, plumbing, etc. This complexity requires space, which is often at a premium. Additionally, such thermodynamic systems may suffer from inherent inefficiencies, resulting in an increase in overall energy consumption.
Complex systems are typically less robust than simple systems. Exotic cooling systems are much more complex, and therefore less robust, than simple forced-air cooling systems. A less robust system has a shorter mean time between failures (MTBF) than a simple system. Exotic cooling systems therefore fail more often than simple forced-air cooling systems.
Besides occurring more often, a failure in an exotic cooling system may be different in kind from a failure in a forced-air system. The failure of an exotic cooling system may result in a destructive thermal cascade failure of the devices cooled by the system.
To compensate for decreased MTBF and to circumvent thermal cascade failure, exotic cooling systems are typically redundant. This redundancy further increases complexity, cost, and power consumption.
A typical Internet server installation may contain many such equipment racks, therefore consuming tens or even hundreds of kilowatts of power. For example, a 4320-channel switching center may have twenty 216-port equipment racks, and would consume in excess of 56 kilowatts for queuing-stage buffers alone. Dissipation of the generated heat from such quantities of power often poses a significant problem.
Additionally, energy costs money. Assuming continuous operation, the 4320-channel switching center consumes in excess of 40,000 kWh (kilowatt-hours) of energy per month for its queuing-stage buffers, which may represent a significant cost.